DS-CDMA transmission method

ABSTRACT

A DS-CDMA transmission method capable of improving the accuracy of channel estimation using pilot symbols by eliminating cross-correlation between pilot symbols inserted into code channels in CDMA multiplexing carrying out fast signal transmission. In each frame assembler, the pilot symbols, which are used for channel estimation for coherent detection, are inserted into coded information data on code channels at fixed intervals, and then the data is modulated by the modulator. The modulated data symbols in each code channel from the modulator are spread by the spreading modulator, the pilot symbols are spread using a spreading code, whereas the information symbols are spread using different spreading codes assigned to respective code channels. The spread signals of the code channels are summed up by the adder to be transmitted.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a direct sequence code divisionmultiple access (DS-CDMA) transmission method carrying out multipleaccess using spread spectrum in mobile communications, and particularlyto a DS-CDMA transmission method that carries out code multiplexing ofmultiple code channels.

2. Description of Related Art

Recently, intensive research and development of the DS-CDMA system havebeen made as one of the next generation mobile communication systems.The DS-CDMA transmission system carries out communications betweenmultiple users using the same frequency band, and individual users areidentified by a spreading code properly assigned to each user.

The DS-CDMA system has advantages over the frequency division multipleaccess or time division multiple access in that it can increase thecapacity in terms of the number of simultaneous subscribers within thesame available frequency band, and is suitable for high speed signaltransmission because it transmits information signals after spreadingthem into wideband signals.

In the mobile communication environment, straight paths between a basestation and mobile stations are seldom unobstructed, therebyconstituting multipath propagation. As a result, the received signalundergoes Rayleigh fading. In Rayleigh fading, the amplitude of areceived signal has Rayleigh distribution, and its phase has a uniformdistribution. It is necessary for a receiver to estimate the randomlyvarying phase of the received signal to carry out coherent detectionwhich is more efficient than differential detection. One of the methodsfor estimating the received phase is implemented by inserting pilotsymbols of a known pattern into information symbols at fixed intervals,and by estimating the received phase of each information symbol on thebasis of the received phases estimated using the pilot symbols. In thiscase, the pilot symbols must be inserted at every time interval duringwhich the phase fluctuation due to fading is nearly negligible.

There are mainly two methods for implementing high bit rate signaltransmission in the DS-CDMA system: (1) a method which varies aspreading factor (processing gain) in accordance with the transmissioninformation rate; and (2) a code multiplexing method which multiplexesmultiple channels each having a fundamental information rate. Here, wewill consider the second method.

FIG. 16 shows a conventional channel structure when carrying out theabsolute coherent detection which makes the channel (amplitude andphase) estimation using the pilot symbols as mentioned above. In thisfigure, N denotes the number of code channels (the number of codemultiplexing). Each code channel is spread using a short code (SC-1, . .. , SC-N) with a period equal to that of information symbol, and isfurther spread using a spreading code referred to as a long code (LC-Y)with a period much longer than that of the common information symbol.The short codes serve to identify the individual code channels, and thelong code serves to distinguish a user from the other simultaneous usersin the same cell in reverse link channels, and from the othersimultaneous users in the other cells in forward link channels. FIG. 17shows a frame structure of a single code channel transmission.

The conventional system has the following problems:

(1) The pilot symbols, which are inserted into each code channel asshown in FIG. 16, are spread by the same spreading code assigned to eachcode channel for spreading data symbols. This results in somecross-correlation between the multiplexed code channels, which degradesthe accuracy of the channel estimation by the pilot symbols. In otherwords, the conventional DS-CDMA code multiplexing method has a problemin that the accuracy of the channel estimation using the pilot symbolsdegrades owing to the cross-correlation between other code channelsbecause the pilot symbols of respective code channels are spread usingdifferent spreading codes. The degradation is remarkable when thereceived signal power per path decreases under the multipathenvironment.

(2) The pilot symbols, which are inserted at the same positions inframes in the respective code channels as shown in FIG. 18A, are used toestimate the received phases for each code channel so as to obtain thetransfer function of the channel on information data sequence by meansof interpolation at the insertion intervals of the pilot symbols asshown in FIG. 18B. This results in a problem in that the accuracy of thechannel estimation degrades with an increase in the fading fluctuationspeed. In addition, since the transmission power control is also carriedout at the insertion intervals of the pilot symbols by measuring thereceived signal power at the positions of the pilot symbols which areinserted in the same positions in the frames of respective code channelsas shown in FIG. 19, there is another problem in that the accuracy ofthe transmission power control also degrades with an increase in thefading fluctuation speed.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a DS-CDMAtransmission method which can improve the accuracy of the channelestimation without much increasing the circuit scale of a transmitterand receiver in the DS-CDMA code multiplexing.

Another object of the present invention is to provide a DS-CDMAtransmission method which can improve the tracking ability to fading ofthe channel estimation and the transmission power control using thepilot symbols without much increasing the circuit scale of thetransmitter and receiver in the DS-CDMA code multiplexing.

According to a first aspect of the present invention, a DS-CDMAtransmission method using a code multiplexing method which transmits asignal by generating a high bit rate transmission channel by codemultiplexing a plurality of code channels, the DS-CDMA transmissionmethod comprises the steps of:

assembling frames for respective code channels by inserting pilotsymbols into information symbols at fixed intervals, the pilot symbolsbeing used for channel estimation for coherent detection;

spreading the information symbols in each of the code channels using aspreading code properly assigned to the each of the code channels, thespreading code being selected from a group of orthogonal spreading codesthat are orthogonal to each other and have a period equal to aninformation symbol period; and

spreading the pilot symbols in the code channels using one of thespreading codes being selected from the group of the orthogonalspreading codes, or any of the spreading codes other than the spreadingcodes assigned to the information symbols in the code channels from thegroup of the orthogonal spreading codes.

According to a second aspect of the present invention, a DS-CDMAtransmission method using a code multiplexing method which transmits asignal by generating a high bit rate transmission channel by codemultiplexing a plurality of code channels, the DS-CDMA transmissionmethod comprises the steps of:

assembling frames for one of the code channels by inserting pilotsymbols into information symbols at fixed intervals, the pilot symbolsbeing used for channel estimation for coherent detection;

spreading the information symbols in each of the code channels using aspreading code properly assigned to the each of the code channels, thespreading code being selected from a group of orthogonal spreading codesthat are orthogonal to each other and have a period equal to aninformation symbol period; and

spreading the pilot symbols, which are generated only in the one of thecode channels, using one of the spreading codes being selected from thegroup of the orthogonal spreading codes, or any of the spreading codesother than the spreading codes assigned to the information symbols inthe code channels from the group of the orthogonal spreading codes.

According to a third aspect of the present invention, a DS-CDMAtransmission method using a code multiplexing method which transmits asignal by generating a high bit rate transmission channel by codemultiplexing a plurality of code channels, the DS-CDMA transmissionmethod comprises the steps of:

convolutionally encoding transmitted data collectively;

writing a convolutionally encoded information data sequence collectivelyat every N×X₂ interval, where N is a number of code channels;

reading, after having written entire information data in Z frames in adirection, where Z is a natural number, the information data in adirection perpendicular to the direction in which the entire informationdata in Z frames are written at every Y₂ interval, where X₂ and Y₂ arenatural numbers that satisfy the relations N×X₂ =Y₂, and N×X₂ ×Y₂ =thetotal number of information data in the Z frames; and

carrying out interleaving that distributes the read information data toN code channels after interleaving.

According to a fourth aspect of the present invention, a DS-CDMAtransmission method using a code multiplexing method which transmits asignal by generating a high bit rate transmission channel by codemultiplexing a plurality of code channels, the DS-CDMA transmissionmethod comprises, when assembling frames for respective code channels byinserting into information symbols pilot symbols used for channelestimation for coherent detection at fixed intervals, the steps of:

dividing N code channels to K blocks each consisting of H code channels,where N is a number of multiplexed code channels, K is a number ofblocks, H is a number of code channels in the block, and N=H×K;

inserting pilot symbols into same positions of frames in the H codechannels in a same block; and

shifting positions of inserting the pilot symbols from block to blocksuch that intervals between closest pilot symbols become uniform withregard to entire pilot symbols in the K blocks.

Here, the DS-CDMA transmission method may further comprise, whencarrying out the channel estimation for the coherent detection using thepilot symbols, the steps of:

obtaining channel estimates at the positions of the pilot symbols in thecode channels using the pilot symbols inserted into the informationsymbols according to a pilot symbol insertion pattern in the block towhich the code channel belongs;

obtaining channel estimates at the positions of the pilot symbols ineach of the blocks by averaging the channel estimates of H code channelsin that block; and

obtaining transfer functions of the code channels on an information datasequence at pilot symbol insertion intervals of the entire pilot symbolsinserted to the entire code channels, the transfer functions beingobtained by interpolation using, in common to the entire code channels,the channel estimates at the positions of the pilot symbols in theblocks.

Here, the DS-CDMA transmission method may further comprise, whenmeasuring received signal power for carrying out transmission powercontrol, the steps of:

measuring the received signal power of the code channels using the pilotsymbols inserted into the information symbols according to a pilotsymbol insertion pattern in the block to which the code channel belongs;

obtaining measured values of the received signal power at the positionsof the pilot symbols in each of the blocks by averaging the measuredreceived signal power of the H code channels in that block; and

carrying out the transmission power control at pilot symbol insertionintervals of the entire pilot symbols distributed to the entire codechannels using, in common to the entire code channels, the measuredvalues of the received signal power at the positions of the pilotsymbols in the blocks.

The above and other objects, effects, features and advantages of thepresent invention will become more apparent from the followingdescription of the embodiments thereof taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a channel structure inthe DS-CDMA transmission system in accordance with the presentinvention;

FIG. 2 is a diagram illustrating another example of a channel structurein the DS-CDMA transmission system in accordance with the presentinvention;

FIG. 3 is a block diagram showing a configuration of an embodiment of anerror correcting encoder in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 4 is a block diagram showing another configuration of an embodimentof an error correcting encoder in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 5 is a block diagram showing a configuration of an embodiment of atransmitter in the DS-CDMA transmission system in accordance with thepresent invention;

FIG. 6 is a block diagram showing a configuration of an embodiment of areceiver in the DS-CDMA transmission system in accordance with thepresent invention;

FIG. 7 is a block diagram showing a configuration of an embodiment of anerror correcting decoder in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 8 is a block diagram showing another configuration of an embodimentof an error correcting decoder in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 9A is a diagram illustrating the operation of an interleaver in theDS-CDMA transmission system in accordance with the present invention;

FIG. 9B is a diagram illustrating the operation of a deinterleaver inthe DS-CDMA transmission system in accordance with the presentinvention;

FIG. 10A is a diagram illustrating the operation of an interleaver inthe DS-CDMA transmission system in accordance with the presentinvention;

FIG. 10B is a diagram illustrating the operation of a deinterleaver inthe DS-CDMA transmission system in accordance with the presentinvention;

FIG. 11 is a diagram illustrating another example of a channel structurein the DS-CDMA transmission system in accordance with the presentinvention;

FIG. 12 illustrates the relationship between FIG. 12A and 12B.

FIG. 12A is a diagram illustrating a pilot symbol insertion pattern(when a block number K=2) in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 12B is a diagram illustrating a channel estimation method (when ablock number K=2) in the DS-CDMA transmission system in accordance withthe present invention;

FIG. 13 is a diagram illustrating transmission power control timings(when a block number K=2) in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 14 illustrates the relationship between FIG. 14A and 14B.

FIG. 14A is a block diagram showing another configuration of theembodiment of the transmitter in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 14B is a block diagram showing another configuration of theembodiment of the transmitter in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 15 illustrates the relationship between FIG. 15A and 15B.

FIG. 15A is a block diagram showing another configuration of theembodiment of the receiver in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 15B is a block diagram showing another configuration of theembodiment of the receiver in the DS-CDMA transmission system inaccordance with the present invention;

FIG. 16 is a diagram illustrating a conventional code multiplexingmethod;

FIG. 17 is a diagram illustrating a frame structure of a single codechannel transmission;

FIG. 18A is a diagram illustrating a conventional pilot symbol insertionpattern;

FIG. 18B is a diagram illustrating a conventional channel estimationmethod;

FIG. 19 is a diagram illustrating conventional transmission powercontrol timings; and

FIG. 20 is a flowchart showing a transmission and reception method inaccordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will now be described with reference to the accompanyingdrawings.

Embodiment 1

FIG. 1 shows an example of a channel structure of a DS-CDMA transmissionsystem in accordance with the present invention. As shown in FIG. 1,each frame of a code channel with a fundamental transmission rate fbconsists of pilot symbols and information data whose information rate isexpanded by spreading factor (processing gain) into a wideband signal.The N code multiplexing of such fundamental channels enables theinformation to be transmitted at the transmission rate of N×fb bps, ifall the channels have the same quality as the fundamental channel. Inthis case, if a common spreading code is used to spread the pilotsymbols of the N code channels, the cross-correlation between theindividual code channels can be eliminated. Since the code channelsundergo the same fading in the multicode multiplex transmission, thesame pilot symbols can be used in common. FIG. 2 illustrates a channelstructure different from that of FIG. 1, in which only one code channeltransmits the pilot symbols.

FIG. 3 is a block diagram showing an error correcting encoder in themulticode multiplex transmission. Input information data is coded by anouter code encoder 1 using an outer code of a concatenated errorcorrecting code, undergoes interleaving by an interleaver 2, and isdistributed to N code channels through a serial-to-parallel converter 3.Subsequently, convolutional coding by a convolutional encoder 4 andinterleaving by an interleaver 5 are carried out successively for eachcode channel. FIG. 9A illustrates an interleaving method of the DS-CDMAtransmission system. The entire information data in Z-frames are writtenin the X₁ data direction for each code channel, and are read in the Y₁data direction perpendicular to the write direction. Here, X₁ and Y₁ arenatural numbers satisfying the relations N×X₁ ×Y₁ =the total number ofinformation data in the Z frames, and X₁ =Y₁.

FIG. 4 shows a configuration of an error correcting encoder of thetransmitter of the DS-CDMA transmission system. As in FIG. 3, the inputinformation data is encoded by an outer code encoder 6 using an outercode of a concatenated error correcting code, and undergoes interleavingby an interleaver 7 to be output. The output data collectively undergo aconvolutional coding by a convolutional encoder 8, and theconvolutionally encoded information sequence is collectively interleavedby an interleaver 9. FIG. 10A illustrates an interleaving method of thepresent DS-CDMA transmission system. The convolutionally encodedinformation data sequence is written at every N×X₂ period, and afterthus writing the entire information data in the Z frames, the data areread at every Y₂ information data period in the direction perpendicularto the write direction. Here, X₂ and Y₂ are natural numbers satisfyingthe relations N×X₂ ×Y₂ =the total number of the information data in theZ frames, and N×X₂ =Y₂.

After that, the interleaved information data are distributed into N codechannels by a serial-to-parallel converter 10.

FIG. 5 is a block diagram showing the transmitter of the DS-CDMAtransmission system. Each frame assembler 11 inserts pilot symbols,which are used for channel estimation for the coherent detection, intothe coded information data of each code channel shown in FIGS. 3 and 4at fixed intervals (the pilot symbols may be inserted into only one codechannel if it is desired to do so). Subsequently, the data are modulatedby each modulator 12. The modulated data symbols of each code channeloutput from each modulator 12 are spread using a spreading code(SC--XxLC--Y) for the pilot symbols, and using spreading codes(SC--PxLC--Y, where P represents 1-N) for the information symbols ofrespective code channels. The spread signals of respective code channelsare summed up by an adder 14 to be transmitted.

FIG. 6 is a block diagram showing a receiver of the DS-CDMA transmissionsystem. The received spread signal is input in common to matched filters15-0, . . . , 15-N corresponding to the spreading codes. The pilotsymbols in the received signal are despread by the matched filter 15-0using the spreading code (SC--XxLC--Y) as the spreading code replica.Then, the received phase of the pilot symbols is estimated by a pilotsymbol channel estimator 16 which averages several pilot symbols usingthe output from a frame synchronizer 17. An information symbol channelestimator 18 estimates the received phase at each position of theinformation symbols by interpolating the estimated information fed fromthe pilot symbol channel estimator 16. Since the code channels in thereceived signal undergo the same fluctuations due to fading, theestimated phase fluctuations in the information symbols can be used incommon to the entire code channels. On the other hand, the informationsymbols on individual code channels are despread by the matched filters15-1-15-N using different spreading codes (SC--PxLC--Y, where P denotes1-N) as spreading code replicas for respective channels. Using thesignal fed from the information symbol channel estimator 18, eachchannel compensator 19 compensates the despread information symbols onthe code channels for the received phase fluctuations which areestimated using the pilot symbols. In a multipath configuration, thephase estimator and compensator (17, 18 and 19), which use pilotchannels corresponding to N code channels as shown in FIG. 6, are usedfor each multipath to be combined. The information symbols fromrespective paths which have been compensated for the fading phasefluctuations by the channel compensator 19 of each channel are RAKEcombined by a RAKE combiner 20 which sums up the multipath componentsusing estimated received complex envelopes of individual paths asweights.

The RAKE combined signals are each input to an error correcting decoderas shown in FIGS. 7 and 8.

FIG. 7 shows a configuration of the error correcting decoder of theDS-CDMA transmission system. The RAKE combined signals are eachdeinterleaved by a deinterleaver 21 separately for each code channel.FIG. 9B illustrates a deinterleaving method of the DS-CDMA transmissionsystem, in which write and read are carried out in the directionsopposite to those in the interleaving method as shown in FIG. 9A. Thedeinterleaved signals are each decoded by a Viterbi decoder 22separately for each channel. The decoded data of the respective codechannels undergo parallel-to-serial conversion by a parallel-to-serialconverter 23, followed by the deinterleave by a deinterleaver 24 and thedecoding by an outer code decoder 25, to be output.

FIG. 8 shows another configuration of the error correcting decoder ofthe DS-CDMA transmission system. The RAKE combined signals of the N codechannels undergo parallel-to-serial conversion by a parallel-to-serialconverter 26, and then are collectively deinterleaved by a deinterleaver27. FIG. 10B illustrates a deinterleaving method of the DS-CDMAtransmission system, in which write and read are carried out in thedirections opposite to those in the interleaving method as shown in FIG.10A. The deinterleaved signals are collectively decoded by a Viterbidecoder 28, followed by the deinterleave by a deinterleaver 29 anddecoding by an outer code decoder 30, to be output.

Embodiment 2

FIG. 11 shows another example of a channel structure of a DS-CDMAtransmission system in accordance with the present invention. As shownin FIG. 11, each frame of a code channel with a fundamental transmissionrate fb consists of pilot symbols and information data whose informationrate is expanded by the spreading factor (processing gain), therebygenerating a wideband signal. The N code multiplexing of suchfundamental channels enables the information to be transmitted at thetransmission rate of N×fb bps, if all the channels have the same qualityas the fundamental channel. Here, the N code channels are divided into Kblocks each consisting of H code channels, where N is the number ofmultiplexed code channels, K is the number of blocks, H is the number ofcode channels in each block, and N=H×K. The integer K may be even orodd. The H code channels in the same block have the pilot symbolsinserted at the same positions in the frames. With regard to the entirepilot symbols in the different K blocks of the code channels, theinserted positions of the pilot symbols in the K blocks are shifted suchthat the intervals become uniform between the closest pilot symbols.

In the present embodiment, the input information data also undergo theerror correcting encoding by the error correcting encoder as shown inFIG. 3. In addition, the data are interleaved by the same method asshown in FIG. 9A.

FIG. 14A and FIG. 14B are block diagrams showing the transmitter of theDS-CDMA transmission system, and FIG. 20 is a flowchart of thetransmission and reception (S200-S250). Each frame assembler 31 insertspilot symbols, which are used for channel estimation for the coherentdetection, into the coded information data of each code channel fed fromthe circuit as shown in FIG. 3, at fixed intervals in accordance with apilot symbol insertion pattern of the block to which the code channelbelongs (S200-S210). The modulated data symbols of the code channelsoutput from respective modulators 32 are separately spread by spreadingmodulators 33 using spreading codes (SC--PxLC--Y, where P represents1-N) assigned to respective code channels (S215). The spread signals ofthe respective code channels are summed up by an adder 34 to betransmitted (S220).

FIG. 15A and FIG. 15B are block diagrams showing a receiver of theDS-CDMA transmission system. The received spread signal is input incommon to matched filters 35 corresponding to the respective spreadingcodes. The pilot symbols and information symbols in the code channelsare despread separately for respective channels by the matched filters35 using the spreading codes (SC--PxLC--Y, where P represents 1-N) asthe spreading code replicas (S225). A demultiplexer (DEMUX) 36corresponding to each code channel extracts from the information symbolsthe pilot symbols inserted into different positions in the respectiveblocks (S230). Then, the received phase of the pilot symbols isestimated by a pilot symbol channel estimator 37 which averagesseparately for each code channel between several pilot symbols using theoutput from a frame synchronizer 38 which carries out coherent detectionof the pilot symbols in response to the output of the matched filter 35(S235). The estimates of the received phase at the pilot symbolpositions in each block are obtained by averaging the estimates of thereceived phase of the code channels in that block (S240). FIG. 12A showsa pilot symbol insertion pattern in each block. An information symbolchannel estimator 39 can obtain transfer functions of the channels onthe information data sequence by making interpolation at every insertioninterval of the entire pilot symbols throughout the entire code channelsby using, in common to all the code channels, the estimates of thereceived phase at the pilot symbol positions of the respective blocks asshown in FIG. 12B (S245). This can improve the tracking ability tofading in the channel estimation because of the reduced interval of theinterpolation in the channel estimation. Using the signal fed from theinformation symbol channel estimator 39, each channel compensator 40compensates the information symbols on the code channels fed from thedemultiplexers 36 for the received phase fluctuations which areestimated using the pilot symbols (S250).

In terms of transmission power control, a received signal power measurer41 measures the received signal power at the pilot symbol positions ofeach code channel on the basis of the signal fed from the pilot symbolchannel estimator 37. Then, it averages in each block the measuredvalues of the received signal power of the code channels belonging tothat block, thereby obtaining the measured values of the received signalpower (SIR) at the pilot symbol positions of the block. A transmissionpower control signal generator 42 generates a transmission power control(TPC) signal based on the measured values. The measured values of thereceived signal power at the pilot symbol positions in respective blocksare used in common to the entire code channels as shown in FIG. 13. Thismakes it possible to achieve the transmission power control at theinsertion intervals of the entire pilot symbols inserted into all thecode channels, and hence to improve the fading tracking ability in thetransmission power control because of the virtually reduced transmissionpower control period.

In a multipath configuration, the phase estimator and compensator (37,38, 39 and 40), which use pilot channels corresponding to N codechannels as shown in FIG. 15, are used for each multipath to becombined. The information symbols from respective paths which have beencompensated for the fading phase fluctuations by each channelcompensator 40 are RAKE combined by each RAKE combiner 43 which sums upthe multipath components using estimated received complex envelopes ofindividual paths as weights. The RAKE combined signals are each input toan error correcting decoder as shown in FIG. 7. Its operation and thedeinterleave method (FIG. 9B) are the same as those of the embodiment 1.

What is claimed is:
 1. A DS-CDMA transmission method using a codemultiplexing method which transmits a signal by generating a high bitrate transmission channel by code multiplexing a plurality of codechannels, said DS-CDMA transmission method comprising, when assemblingframes for respective code channels by inserting into informationsymbols pilot symbols used for channel estimation for coherent detectionat fixed intervals, the steps of:dividing N code channels to K blockseach consisting of H code channels, where N is a number of multiplexedcode channels, K is a number of blocks, H is a number of code channelsin the block, and N=H×K; inserting pilot symbols into same positions offrames in the H code channels in a same block; and shifting positions ofinserting said pilot symbols from block to block such that intervalsbetween closest pilot symbols become uniform with regard to entire pilotsymbols in the K blocks.
 2. The DS-CDMA transmission method as claimedin claim 1, further comprising, when carrying out the channel estimationfor the coherent detection using said pilot symbols, the stepsof:obtaining channel estimates at the positions of said pilot symbols insaid code channels using said pilot symbols inserted into saidinformation symbols according to a pilot symbol insertion pattern in theblock to which said code channel belongs; obtaining channel estimates atthe positions of said pilot symbols in each of said blocks by averagingsaid channel estimates of H code channels in that block; and obtainingtransfer functions of said code channels on an information data sequenceat pilot symbol insertion intervals of the entire pilot symbols insertedto the entire code channels, said transfer functions being obtained byinterpolation using, in common to the entire code channels, said channelestimates at the positions of said pilot symbols in said blocks.
 3. TheDS-CDMA transmission method as claimed in claim 1, further comprising,when measuring received signal power for carrying out transmission powercontrol, the steps of:measuring said received signal power of said codechannels using said pilot symbols inserted into said information symbolsaccording to a pilot symbol insertion pattern in the block to which saidcode channel belongs; obtaining measured values of said received signalpower at the positions of said pilot symbols in each of said blocks byaveraging the measured received signal power of said H code channels inthat block; and carrying out said transmission power control at pilotsymbol insertion intervals of the entire pilot symbols distributed tothe entire code channels using, in common to the entire code channels,said measured values of said received signal power at the positions ofsaid pilot symbols in said blocks.
 4. A DS-CDMA transmission methodusing a code multiplexing method which transmits a signal by generatinga high bit rate transmission channel by code multiplexing a plurality ofcode channels, said DS-CDMA transmission method comprising the stepsof:assembling frames for respective code channels by inserting pilotsymbols into information symbols at fixed intervals, said pilot symbolsbeing used for channel estimation for coherent detection; spreading saidinformation symbols in each of said code channels using a spreading codeproperly assigned to said each of said code channels, said spreadingcode being selected from a group of orthogonal spreading codes that areorthogonal to each other and have a period equal to an informationsymbol period; and spreading said pilot symbols in said code channelsusing one of the spreading codes being selected from said group of saidorthogonal spreading codes, or any of the spreading codes other than thespreading codes assigned to said information symbols in said codechannels from said group of said orthogonal spreading codes; wherein theinformation symbols in a plurality of code channels are spreaded byspreading codes which are different from each other, the pilot symbolsin a plurality of code channels are spreaded by the same one spreadingcode, and the pilot symbols are inserted into the same bit position inall the multiplexed code channels.
 5. A DS-CDMA transmission methodusing a code multiplexing method which transmits a signal by generatinga high bit rate transmission channel by code multiplexing a plurality ofcode channels, said DS-CDMA transmission method comprising the stepsof:assembling frames for one of said code channels by inserting pilotsymbols into information symbols at fixed intervals, said pilot symbolsbeing used for channel estimation for coherent detection; spreading saidinformation symbols in each of said code channels using a spreading codeproperly assigned to said each of said code channels, said spreadingcode being selected from a group of orthogonal spreading codes that areorthogonal to each other and have a period equal to an informationsymbol period; and spreading said pilot symbols, which are generatedonly in said one of said code channels, using one of the spreading codesbeing selected from said group of said orthogonal spreading codes, orany of the spreading codes other than the spreading codes assigned tosaid information symbols in said code channels from said group of saidorthogonal spreading codes; wherein the information symbols in aplurality of code channels are spreaded by spreading codes which aredifferent from each other, the pilot symbols in a plurality of codechannels are spreaded by the same one spreading code, and the pilotsymbols are inserted into the same bit position in all the multiplexedcode channels.
 6. A DS-CDMA transmission method using a codemultiplexing method which transmits a high bit rate transmission signalby modulating information symbols by a high bit rate spreading codethrough the N code channels, said DS-CDMA transmission method comprisingthe steps of:assembling frames for respective on of said N code channelsby inserting a pilot symbol into the same one bit position of M codechannel (1≦M≦N) among the N code channels, said pilot symbol being usedfor channel estimation for coherent detection; spreading the informationsymbols in said N code channels, respectively, using spreading codeswhich are different from each other among said N code channels; andspreading said M pilot symbols in said M code channels using the sameone spreading code.